title: Structural analysis for glycolipid recognition by the C-type lectins Mincle and MCL.
abstract: Mincle [macrophage inducible Ca(2+)-dependent (C-type) lectin; CLEC4E] and MCL (macrophage C-type lectin; CLEC4D) are receptors for the cord factor TDM (trehalose-6,6'-dimycolate), a unique glycolipid of mycobacterial cell-surface components, and activate immune cells to confer adjuvant activity. Although it is known that receptor-TDM interactions require both sugar and lipid moieties of TDM, the mechanisms of glycolipid recognition by Mincle and MCL remain unclear. We here report the crystal structures of Mincle, MCL, and the Mincle-citric acid complex. The structures revealed that these receptors are capable of interacting with sugar in a Ca(2+)-dependent manner, as observed in other C-type lectins. However, Mincle and MCL uniquely possess shallow hydrophobic regions found adjacent to their putative sugar binding sites, which reasonably locate for recognition of fatty acid moieties of glycolipids. Functional studies using mutant receptors as well as glycolipid ligands support this deduced binding mode. These results give insight into the molecular mechanism of glycolipid recognition through C-type lectin receptors, which may provide clues to rational design for effective adjuvants.
authors.affiliation: Laboratory of Biomolecular Science, Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo 060-0812, Japan.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Furukawa
authors.forename: Jun
authors.initials: J
authors.lastname: Kamishikiryo
authors.forename: Daiki
authors.initials: D
authors.lastname: Mori
authors.forename: Kenji
authors.initials: K
authors.lastname: Toyonaga
authors.forename: Yuki
authors.initials: Y
authors.lastname: Okabe
authors.forename: Aya
authors.initials: A
authors.lastname: Toji
authors.forename: Ryo
authors.initials: R
authors.lastname: Kanda
authors.forename: Yasunobu
authors.initials: Y
authors.lastname: Miyake
authors.forename: Toyoyuki
authors.initials: T
authors.lastname: Ose
authors.forename: Sho
authors.initials: S
authors.lastname: Yamasaki
authors.forename: Katsumi
authors.initials: K
authors.lastname: Maenaka
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites / Q000235:genetics; D002118:Calcium / Q000737:chemistry / Q000378:metabolism; D019343:Citric Acid / Q000737:chemistry / Q000378:metabolism; D003311:Cord Factors / Q000737:chemistry* / Q000378:metabolism; D018360:Crystallography, X-Ray; D006801:Humans; D037181:Lectins, C-Type / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D008024:Ligands; D051379:Mice; D008969:Molecular Sequence Data; D009154:Mutation; D011485:Protein Binding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011971:Receptors, Immunologic / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D020349:Surface Plasmon Resonance
chemical_list: C482593:CLEC4D protein, human; D003311:Cord Factors; D037181:Lectins, C-Type; D008024:Ligands; D011971:Receptors, Immunologic; D019343:Citric Acid; D002118:Calcium
keywords: X-ray crystallography; innate immunity; mycobacteria; myeloid cells; pattern-recognition receptors